On translational regulation and EMT

Non-canonical mRNA translation initiation in cell stress and cancer

The now well described canonical mRNA translation initiation mechanism of m7G 'cap' recognition by cap-binding protein eIF4E and assembly of the canonical pre-initiation complex consisting of scaffolding protein eIF4G and RNA helicase eIF4A has historically been thought to describe all cellular mRNA translation. However, the past decade has seen the discovery of alternative mechanisms to canonical eIF4E mediated mRNA translation initiation. Studies have shown that non-canonical alternate mechanisms of cellular mRNA translation initiation, whether cap-dependent or independent, serve to provide selective translation of mRNAs under cell physiological and pathological stress conditions. These conditions typically involve the global downregulation of canonical eIF4E1/cap-mediated mRNA translation, and selective translational reprogramming of the cell proteome, as occurs in tumor development and malignant progression. Cancer cells must be able to maintain physiological plasticity to acquire a migratory phenotype, invade tissues, metastasize, survive and adapt to severe microenvironmental stress conditions that involve inhibition of canonical mRNA translation initiation. In this review we describe the emerging, important role of non-canonical, alternate mechanisms of mRNA translation initiation in cancer, particularly in adaptation to stresses and the phenotypic cell fate changes involved in malignant progression and metastasis. These alternate translation initiation mechanisms provide new targets for oncology therapeutics development.

Breast cancer cell mesenchymal transition and metastasis directed by DAP5/eIF3d-mediated selective mRNA translation

Cancer cell plasticity enables cell survival in harsh physiological environments and fate transitions such as the epithelial-to-mesenchymal transition (EMT) that underlies invasion and metastasis. Using genome-wide transcriptomic and translatomic studies, an alternate mechanism of cap-dependent mRNA translation by the DAP5/eIF3d complex is shown to be essential for metastasis, EMT, and tumor directed angiogenesis. DAP5/eIF3d carries out selective translation of mRNAs encoding EMT transcription factors and regulators, cell migration integrins, metalloproteinases, and cell survival and angiogenesis factors. DAP5 is overexpressed in metastatic human breast cancers associated with poor metastasis-free survival. In human and murine breast cancer animal models, DAP5 is not required for primary tumor growth but is essential for EMT, cell migration, invasion, metastasis, angiogenesis, and resistance to anoikis. Thus, cancer cell mRNA translation involves two cap-dependent mRNA translation mechanisms, eIF4E/mTORC1 and DAP5/eIF3d. These findings highlight a surprising level of plasticity in mRNA translation during cancer progression and metastasis.

Heterogeneity and dynamic of EMT through the plasticity of ribosome and mRNA translation

Growing evidence exposes translation and its translational machinery as key players in establishing and maintaining physiological and pathological biological processes. Examining translation may not only provide new biological insight but also identify novel innovative therapeutic targets in several fields of biology, including that of epithelial-to-mesenchymal transition (EMT). EMT is currently considered as a dynamic and reversible transdifferentiation process sustaining the transition from an epithelial to mesenchymal phenotype, known to be mainly driven by transcriptional reprogramming. However, it seems that the characterization of EMT plasticity is challenging, relying exclusively on transcriptomic and epigenetic approaches. Indeed, heterogeneity in EMT programs was reported to depend on the biological context. Here, by reviewing the involvement of translational control, translational machinery and ribosome biogenesis characterizing the different types of EMT, from embryonic and adult physiological to pathological contexts, we discuss the added value of integrating translational control and its machinery to depict the heterogeneity and dynamics of EMT programs.

RNA-Binding Protein La Mediates TGFβ-Induced Epithelial to Mesenchymal Transition and Cancer Stem Cell Properties

Simple Summary

Reversible epithelial to mesenchymal transition (EMT) plays a key role in establishing a malignant phenotype by assuring cancer cell plasticity critical for cancer progression by allowing a small fraction of cancer cells to detach from primary lesions and outgrow at metastatic sites. Cancer cell plasticity is associated with cancer stem cell properties contributing to chemoresistance, metastasis, and poor clinical outcomes. Dysregulated RNA-binding proteins are key players in controlling the RNA metabolism, including mRNA processing, export, and translation, and have been implicated in cancer cell plasticity. In this study, we demonstrated that aberrantly expressed RNA-binding protein La is critical for transforming growth factor β-induced EMT and for gaining cancer stem cell properties. Understanding the function of aberrant RNA-binding protein expression in cancer cell plasticity reveals prospects for identifying novel therapeutic targets.

Abstract

Background: the aberrant overexpression of predominantly nuclear localizing RNA-binding protein (RBP) La contributes to proliferation, mobility, and chemoresistance of cancer cells and tumor growth in mice. Methods: studies included cancer tissue microarrays (TMAs) analyses, cancer tissue data mining, transforming growth factor β (TGFβ)-induced cancer cell plasticity studies, three dimensional sphere growth, epithelial to mesenchymal transition (EMT) assays, analysis of cancer stem cell (CSC) marker expression, and post-translational modification of cancer-associated La protein. Results: we demonstrated that significant overexpression of RBP La in lung and head and neck cancer tissue correlates with poor overall survival. Furthermore, small interfering RNA-mediated depletion of La reduced proliferation and migration of cancer cells, blocked TGFβ-induced EMT, and diminished both EMT and CSC marker expression. Rescue experiments with La wildtype but not RNA chaperone domain activity-defective La mutant increased the expression of those cancer progression markers, suggesting a critical role of La’s RNA chaperone activity in this process. La depletion in cancer cells also significantly decreased sphere growth in the presence of TGFβ. Interestingly, TGFβ treatment induced phosphorylation of La at threonine 389 (pLa^T389) only in adherents but not in 3D growing cultures. Conclusion: our study suggests that the TGFβ/AKT/pLa^T389 signaling pathway regulates cancer cell plasticity.

MicroRNA-381-A Key Transcriptional Regulator: Its Biological Function and Clinical Application Prospects in Cancer

MicroRNAs (miRNAs) are small non-coding RNA molecules that function by regulating messenger RNAs. Recent studies have shown that miRNAs play important roles in multiple processes of cancer development. MiR-381 is one of the most important miRNAs in cancer progression. MiR-381 is downregulated in some cancers and upregulated in other cancers, including glioma, epithelial sarcoma, and osteosarcoma. MiR-381 regulates epithelial-mesenchymal transition (EMT), chemotherapeutic resistance, radioresistance, and immune responses. Thus, miR-381 participates in tumor initiation, progression, and metastasis. Moreover, miR-381 functions in various oncogenic pathways, including the Wnt/β-catenin, AKT, and p53 pathways. Clinical studies have shown that miR-381 could be considered a biomarker or a novel prognostic factor. Here, we summarize the present studies on the role of miR-381 in cancer development, including its biogenesis and various affected signaling pathways, and its clinical application prospects. MiR-381 expression is associated with tumor stage and survival time, making miR-381 a novel prognostic factor.

Dehydroandrographolide Inhibits Osteosarcoma Cell Growth and Metastasis by Targeting SATB2-mediated EMT

BACKGROUND

The 12-hydroxy-14-dehydroandrographolide (DP) is a predominant component of the traditional herbal medicine Andrographis paniculata (Burm. f.) Nees (Acanthaceae). Recent studies have shown that DP exhibits potent anti-cancer effects against oral and colon cancer cells.

OBJECTIVE

This investigation examined the potential effects of DP against osteosarcoma cell.

METHODS

A cell analyzer was used to measure cell viability. The cell growth and proliferation were performed by Flow cytometry and BrdU incorporation assay. The cell migration and invasion were determined by wound healing and transwell assay. The expression of EMT related proteins was examined by Western blot analysis.

RESULTS

In this study, we found that DP treatment repressed osteosarcoma (OS) cell growth in a dose-dependent manner. DP treatment significantly inhibited OS cell proliferation by arresting the cell cycle at G2/M phase. In addition, DP treatment effectively inhibited the migration and invasion abilities of OS cells through wound healing and Transwell tests. Mechanistic studies revealed that DP treatment effectively rescued the epithelialmesenchymal transition (EMT), while forced expression of SATB2 in OS cells markedly reversed the pharmacological effect of DP on EMT.

CONCLUSION

Our data demonstrated that DP repressed OS cell growth through inhibition of proliferation and cell cycle arrest; DP also inhibited metastatic capability of OS cells through a reversal of EMT by targeting SATB2. These findings demonstrate DP's potential as a therapeutic drug for OS treatment.

Ribosomes as a nexus between translation and cancer progression: Focus on ribosomal Receptor for Activated C Kinase 1 (RACK1) in breast cancer

Ribosomes coordinate spatiotemporal control of gene expression, contributing to the acquisition and maintenance of cancer phenotype. The link between ribosomes and cancer is found in the roles of individual ribosomal proteins in tumorigenesis and cancer progression, including the ribosomal protein, receptor for activated C kinase 1 (RACK1). RACK1 regulates cancer cell invasion and is localized in spreading initiation centres, structural adhesion complexes containing RNA binding proteins and poly-adenylated mRNAs that suggest a local translation process. As RACK1 is a ribosomal protein directly involved in translation and in breast cancer progression, we propose a new molecular mechanism for breast cancer cell migration and invasion, which considers the molecular differences between epithelial and mesenchymal cell profiles in order to characterize and provide novel targets for therapeutic strategies. Hence, we provide an analysis on how ribosomes translate cancer progression with a final focus on the ribosomal protein RACK1 in breast cancer.

Role of the RNA-binding protein La in cancer pathobiology

RNA-binding proteins are important regulators of RNA metabolism and are of critical importance in all steps of the gene expression cascade. The role of aberrantly expressed RBPs in human disease is an exciting research field and the potential application of RBPs as a therapeutic target or a diagnostic marker represents a fast-growing area of research.Aberrant overexpression of the human RNA-binding protein La has been found in various cancer entities including lung, cervical, head and neck, and chronic myelogenous leukaemia. Cancer-associated La protein supports tumour-promoting processes such as proliferation, mobility, invasiveness and tumour growth. Moreover, the La protein maintains the survival of cancer cells by supporting an anti-apoptotic state that may cause resistance to chemotherapeutic therapy.The human La protein represents a multifunctional post-translationally modified RNA-binding protein with RNA chaperone activity that promotes processing of non-coding precursor RNAs but also stimulates the translation of selective messenger RNAs encoding tumour-promoting and anti-apoptotic factors. In our model, La facilitates the expression of those factors and helps cancer cells to cope with cellular stress. In contrast to oncogenes, able to initiate tumorigenesis, we postulate that the aberrantly elevated expression of the human La protein contributes to the non-oncogenic addiction of cancer cells. In this review, we summarize the current understanding about the implications of the RNA-binding protein La in cancer progression and therapeutic resistance. The concept of exploiting the RBP La as a cancer drug target will be discussed.

Fine-tuning the metabolic rewiring and adaptation of translational machinery during an epithelial-mesenchymal transition in breast cancer cells

ABSTRACT

BACKGROUND

During breast cancer progression, the epithelial to mesenchymal transition has been associated with metastasis and endocrine therapy resistance; however, the underlying mechanisms remain elusive. To gain insight into this process, we studied the transition undergone by MCF7-derived cells, which is driven by the constitutive nuclear expression of a MKL1 variant devoid of the actin-binding domain (MKL1 ΔN200). We characterized the adaptive changes that occur during the MKL1-induced cellular model and focused on regulation of translation machinery and metabolic adaptation.

METHODS

We performed a genome-wide analysis at the transcriptional and translational level using ribosome profiling complemented with RNA-Seq and analyzed the expression of components of the translation machinery and enzymes involved in energy metabolism. NGS data were correlated with metabolomic measurements and quantification of specific mRNAs extracted from polysomes and western blots.

RESULTS

Our results reveal the expression profiles of a luminal to basal-like state in accordance with an epithelial to mesenchymal transition. During the transition, the synthesis of ribosomal proteins and that of many translational factors was upregulated. This overexpression of the translational machinery appears to be regulated at the translational level. Our results indicate an increase of ribosome biogenesis and translation activity. We detected an extensive metabolic rewiring occurring in an already "Warburg-like" context, in which enzyme isoform switches and metabolic shunts indicate a crucial role of HIF-1α along with other master regulatory factors. Furthermore, we detected a decrease in the expression of enzymes involved in ribonucleotide synthesis from the pentose phosphate pathway. During this transition, cells increase in size, downregulate genes associated with proliferation, and strongly upregulate expression of cytoskeletal and extracellular matrix genes.

CONCLUSIONS

Our study reveals multiple regulatory events associated with metabolic and translational machinery adaptation during an epithelial mesenchymal-like transition process. During this major cellular transition, cells achieve a new homeostatic state ensuring their survival. This work shows that ribosome profiling complemented with RNA-Seq is a powerful approach to unveil in-depth global adaptive cellular responses and the interconnection among regulatory circuits, which will be helpful for identification of new therapeutic targets.

Ribosome biogenesis during cell cycle arrest fuels EMT in development and disease

Ribosome biogenesis is a canonical hallmark of cell growth and proliferation. Here we show that execution of Epithelial-to-Mesenchymal Transition (EMT), a migratory cellular program associated with development and tumor metastasis, is fueled by upregulation of ribosome biogenesis during G1/S arrest. This unexpected EMT feature is independent of species and initiating signal, and is accompanied by release of the repressive nucleolar chromatin remodeling complex (NoRC) from rDNA, together with recruitment of the EMT-driving transcription factor Snai1 (Snail1), RNA Polymerase I (Pol I) and the Upstream Binding Factor (UBF). EMT-associated ribosome biogenesis is also coincident with increased nucleolar recruitment of Rictor, an essential component of the EMT-promoting mammalian target of rapamycin complex 2 (mTORC2). Inhibition of rRNA synthesis in vivo differentiates primary tumors to a benign, Estrogen Receptor-alpha (ERα) positive, Rictor-negative phenotype and reduces metastasis. These findings implicate the EMT-associated ribosome biogenesis program with cellular plasticity, de-differentiation, cancer progression and metastatic disease.

Sika deer (Cervus nippon) velvet antler extract attenuates prostate cancer in xenograft model

The present study determines whether antler extract (AE) possesses inhibitory effects in a prostate cancer (PC) xenograft model and explores the underlying mechanism. After therapeutic intervention for two weeks, AE significantly inhibited prostate cancer xenograft tumor growth by 65.08%, and prostate-specific antigen (PSA) and serum dihydrotestosterone (DHT) levels. However, AE increased the serum testosterone level compared to the vehicle control group. Furthermore, our investigation of the inhibitory effects on angiogenesis and epithelial-to-mesenchymal transition (EMT)-related genes revealed that AE downregulated matrix metalloproteinase 2 (MMP)-2, (MMP)-9, vascular endothelial growth factor (VEGF), zinc finger protein (SNAIL1), twist-related protein 1 (TWIST1), and zinc-finger E-box-binding homeobox 1 (ZEB1) in vivo. In contrast, AE increased tissue inhibitor of MMP (TIMP)-1, (TIMP)-2, and E-cadherin. The results suggest that AE possesses potent anti-PC activity, and this is the first report on the anti-PC effect of AE in vivo.

Farrerol overcomes the invasiveness of lung squamous cell carcinoma cells by regulating the expression of inducers of epithelial mesenchymal transition

In recent years Epithelial Mesenchymal Transition (EMT) has been proposed as a mechanism indispensable to acquisition of metastatic properties by tumor cells. In this study we tested the ability of Farrerol, a Chinese herb-derived compound to ablate the EMT in human lung squamous cell carcinoma cells. Human lung squamous cell carcinoma cells, Calu-1 were treated with various concentrations of Farrerol for 24 h to examine its effect on their viability by the MTT assay. Only those concentrations which showed least effect on the viability of Calu-1 cells were further used to evaluate the expression of epithelial and mesenchymal markers by western blotting. Furthermore the effect of such concentrations on the migration and invasion of Calu-1 cells was determined by wound healing and transwell invasion assays respectively. The results demonstrated that Farrerol treatment led to the downregulation of Slug and Zeb-1, transcriptional regulators of EMT with the concomitant increase and decrease in the expression of E-cadherin and vimentin respectively. These data were further supported by migration and invasion assays which demonstrated that Farrerol treatment caused inhibited the migration and invasion of Calu-1 lung squamous cell carcinoma cells. Taken together, our results indicate that Farrerol suppresses lung squamous cell carcinoma cell metastatic potential by modulating the expression of EMT proteins.

Translational control of aberrant stress responses as a hallmark of cancer

Altered mRNA translational control is emerging as a critical factor in cancer development and progression. Targeting specific elements of the translational machinery, such as mTORC1 or eIF4E, is emerging as a new strategy for innovative cancer therapy. While translation of most mRNAs takes place through cap-dependent mechanisms, a sub-population of cellular mRNA species, particularly stress-inducible mRNAs with highly structured 5'-UTR regions, are primarily translated through cap-independent mechanisms. Intriguingly, many of these mRNAs encode proteins that are involved in tumour cell adaptation to microenvironmental stress, and thus linked to aggressive behaviour including tumour invasion and metastasis. This necessitates a rigorous search for links between microenvironmental stress and aggressive tumour phenotypes. Under stress, cells block global protein synthesis to preserve energy while maintaining selective synthesis of proteins that support cell survival. One highly conserved mechanism to regulate protein synthesis under cell stress is to sequester mRNAs into cytosolic aggregates called stress granules (SGs), where their translation is silenced. SGs confer survival advantages and chemotherapeutic resistance to tumour cells under stress. Recently, it has been shown that genetically blocking SG formation dramatically reduces tumour invasive and metastatic capacity in vivo. Therefore, targeting SG formation might represent a potential treatment strategy to block cancer metastasis. Here, we present the critical link between selective mRNA translation, stress adaptation, SGs, and tumour progression. Further, we also explain how deciphering mechanisms of selective mRNA translation occurs under cell stress holds great promise for the identification of new targets in the treatment of cancer. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Ferrerol overcomes the invasiveness of lung squamous cell carcinoma cells by regulating the expression of inducers of Epithelial Mesenchymal Transition

In recent years Epithelial Mesenchymal Transition (EMT) has been proposed as a mechanism indispensable to acquisition of metastatic properties by tumor cells. In this study we tested the ability of Ferrerol, a Chinese herb-derived compound to ablate the EMT in human lung squamous cell carcinoma cells. Human lung squamous cell carcinoma cells, Calu-1 were treated with various concentrations of Ferrerol for 24 h to examine its effect on their viability by the MTT assay. Only those concentrations which showed least effect on the viability of Calu-1 cells were further used to evaluate the expression of epithelial and mesenchymal markers by western blotting. Furthermore the effect of such concentrations on the migration and invasion of Calu-1 cells was determined by wound healing and transwell invasion assays respectively. The results demonstrated that Ferrerol treatment led to the downregulation of Slug and Zeb-1, transcriptional regulators of EMT with the concomitant increase and decrease in the expression of E-cadherin and vimentin respectively. These data were further supported by migration and invasion assays which demonstrated that Ferrerol treatment caused inhibited the migration and invasion of Calu-1 lung squamous cell carcinoma cells. Taken together, our results indicate that Ferrerol suppresses lung squamous cell carcinoma cell metastatic potential by modulating the expression of EMT proteins.

RIG-I Resists Hypoxia-Induced Immunosuppression and Dedifferentiation

A hypoxic tumor microenvironment is linked to poor prognosis. It promotes tumor cell dedifferentiation and metastasis and desensitizes tumor cells to type-I IFN, chemotherapy, and irradiation. The cytoplasmic immunoreceptor retinoic acid-inducible gene-I (RIG-I) is ubiquitously expressed in tumor cells and upon activation by 5'-triphosphate RNA (3pRNA) drives the induction of type I IFN and immunogenic cell death. Here, we analyzed the impact of hypoxia on the expression of RIG-I in various human and murine tumor and nonmalignant cell types and further investigated its function in hypoxic murine melanoma. 3pRNA-inducible RIG-I-expression was reduced in hypoxic melanoma cells compared with normoxic controls, a phenomenon that depended on the hypoxia-associated transcription factor HIF1α. Still, RIG-I functionality was conserved in hypoxic melanoma cells, whereas responsiveness to recombinant type-I IFN was abolished, due to hypoxia-induced loss of type I IFN receptor expression. Likewise, RIG-I activation in hypoxic melanoma cells, but not exposure to recombinant IFNα, provoked melanocyte antigen-specific CD8⁺ T-cell and NK-cell attack. Scavenging of hypoxia-induced reactive oxygen species by vitamin C restored the inducible expression of RIG-I under hypoxia in vitro, boosted in vitro anti-melanoma NK- and CD8⁺ T-cell attack, and augmented 3pRNA antitumor efficacy in vivo These results demonstrate that RIG-I remains operational under hypoxia and that RIG-I function is largely insensitive to lower cell surface expression of the IFNα receptor. RIG-I function could be fortified under hypoxia by the combined use of 3pRNA with antioxidants. Cancer Immunol Res; 5(6); 455-67. ©2017 AACR.

Positive feedback loop of YB-1 interacting with Smad2 promotes liver fibrosis

Y-box binding protein (YB-1), known as a multifunctional cellular protein in various biological processes, was recently reported to be associated with liver fibrosis. The critical role of TGF-β/Smad signaling pathway in stimulating the transcription of fibrotic genes in fibroblasts have already been identified, however, whether and how YB-1 modulated liver fibrosis via TGF-β/Smad signaling pathway remains largely unknown. In our previous study, we proved that ectopic TGF-β was associated with YB-1 expression. Herein, by combining in vitro experiments in LX2 human hepatic stellate cells and in vivo studies by building CCl4 based mice liver fibrosis model, we showed that YB-1 and p-YB-1 were upregulated in liver fibrosis tissue, and YB-1 promoted the deposition of excess extracellular matrix. Mechanistically, Smad2, a key member in TGF-β signaling pathway, acted as a transcription factor that triggered YB-1 promoter, while on the other hand, p-YB-1 stabilized Smad2 by attenuating its ubiquitination. Knockdown of Smad2 could reduce YB-1 expression, which in turn shorter the half time of Smad2. Furthermore, the serine102 residue of YB-1 both affected its binding and stabilizing activity to Smad2. These finding demonstrated that YB-1 and Smad2 played as a positive feedback loop in promoting liver fibrosis. In conclusion, TGF-β signaling pathway may influence liver fibrosis by incorporating with YB-1, indicating that YB-1 could be a potential target for therapies against liver fibrosis.

Interplay between YB-1 and IL-6 promotes the metastatic phenotype in breast cancer cells

Epithelial to mesenchymal transition (EMT) induces cell plasticity and promotes metastasis. The multifunctional oncoprotein Y-box binding protein-1 (YB-1) and the pleiotropic cytokine interleukin 6 (IL-6) have both been implicated in tumor cell metastasis and EMT, but via distinct pathways. Here, we show that direct interplay between YB-1 and IL-6 regulates breast cancer metastasis. Overexpression of YB-1 in breast cancer cell lines induced IL-6 production while stimulation with IL-6 increased YB-1 expression and YB-1 phosphorylation. Either approach was sufficient to induce EMT features, including increased cell migration and invasion. Silencing of YB-1 partially reverted the EMT and blocked the effect of IL-6 while inhibition of IL-6 signaling blocked the phenotype induced by YB-1 overexpression, demonstrating a clear YB-1/IL-6 interdependence. Our findings describe a novel signaling network in which YB-1 regulates IL-6, and vice versa, creating a positive feed-forward loop driving EMT-like metastatic features during breast cancer progression. Identification of signaling partners or pathways underlying this co-dependence may uncover novel therapeutic opportunities.

The human NANOS3 gene contributes to lung tumour invasion by inducing epithelial-mesenchymal transition

We have explored the role of the human NANOS3 gene in lung tumour progression. We show that NANOS3 is over-expressed by invasive lung cancer cells and is a prognostic marker for non-small cell lung carcinomas (NSCLCs). NANOS3 gene expression is restricted in testis and brain and is regulated by epigenetic events. It is up-regulated in cultured cells undergoing epithelial - mesenchymal transition (EMT). NANOS3 over-expression in human NSCLC cell lines enhances their invasiveness by up-regulating EMT, whereas its silencing induces mesenchymal - epithelial transition. NANOS3 represses E-cadherin at the transcriptional level and up-regulates vimentin post-transcriptionally. Also, we show that NANOS3 binds mRNAs encoding vimentin and regulates the length of their poly(A) tail. Finally, NANOS3 can also protect vimentin mRNA from microRNA-mediated repression. We thus demonstrate a role for NANOS3 in the acquisition of invasiveness by human lung tumour cells and propose a new mechanism of post-transcriptional regulation of EMT.

YB-1 expression promotes epithelial-to-mesenchymal transition in prostate cancer that is inhibited by a small molecule fisetin

Epithelial-to-mesenchymal transition (EMT) plays an important role in prostate cancer (PCa) metastasis. The transcription/translation regulatory Y-box binding protein-1 (YB-1) is known to be associated with cancer metastasis. We observed that YB-1 expression increased with tumor grade and showed an inverse relationship with E-cadherin in a human PCa tissue array. Forced YB-1 expression induced a mesenchymal morphology that was associated with down regulation of epithelial markers. Silencing of YB-1 reversed mesenchymal features and decreased cell proliferation, migration and invasion in PCa cells. YB-1 is activated directly via Akt mediated phosphorylation at Ser102 within the cold shock domain (CSD). We next identified fisetin as an inhibitor of YB-1 activation. Computational docking and molecular dynamics suggested that fisetin binds on the residues from β1 - β4 strands of CSD, hindering Akt's interaction with YB-1. Calculated free binding energy ranged from -11.9845 to -9.6273 kcal/mol. Plasmon Surface Resonance studies showed that fisetin binds to YB-1 with an affinity of approximately 35 µM, with both slow association and dissociation. Fisetin also inhibited EGF induced YB-1 phosphorylation and markers of EMT both in vitro and in vivo. Collectively our data suggest that YB-1 induces EMT in PCa and identify fisetin as an inhibitor of its activation.

Alternative forms of Y-box binding protein 1 and YB-1 mRNA

The multifunctional eukaryotic protein YB-1 (Y-box binding protein 1) plays a role in DNA reparation, transcription regulation, splicing, and mRNA translation, thereby participating in many crucial events in cells. Its effect is dependent mostly on its amount, and hence, on regulation of its synthesis. Published data on regulation of synthesis of YB-1 mediated by its mRNA 5' UTR, and specifically on the 5' UTR length and the presence of TOP-like motifs in this region, are contradictory. Here we report that 5' UTRs of major forms of human, rabbit, and mouse YB-1 mRNAs are about 140 nucleotides long and contain no TOP-like motifs mentioned in the literature. Also, we have found that YB-1 specifically interacts with the 5' UTR of its own mRNA within a region of about 100 nucleotides upstream from the start codon. Apart from YB-1, translation of YB-1 mRNA in a cell free system gives an additional product with an extended N-terminus and lower electrophoretic mobility. The start codon for synthesis of the additional product is AUC at position -(60-58) of the same open reading frame as that for the major product. Also, in the cell there is an alternative YB-1 mRNA with exon 1 replaced by a part of intron 1; YB-1 synthesized in vitro from this mRNA contains, instead of its N-terminal A/P domain, 10-11 amino acids encoded by intron 1.

A novel anti‑cancer effect of resveratrol: reversal of epithelial‑mesenchymal transition in prostate cancer cells

Carcinoma progression is associated with the loss of epithelial features and the acquisition of a mesenchymal phenotype, a process known as epithelial-mesenchymal transition (EMT). Resveratrol, a natural polyphenolic compound found in grapes, berries and peanuts, has a wide range of pharmacological properties, including anti-tumor metastasis properties. The underlying mechanism through which resveratrol inhibits metastasis of prostate cancer (PCa) is not yet fully understood; however, it is thought to be associated with the disruption of EMT. In the present study, lipopolysaccharide (LPS) was used to trigger EMT in PC-3 and LNCaP PCa cell lines, and the cell lines were subsequently treated with resveratrol. The results demonstrated that exposure of PC-3 and LNCaP cells to LPS resulted in morphological alterations characteristic of EMT, as well as an increase in the expression of the mesenchymal marker vimentin and a decrease in the expression of E-cadherin. In addition, LPS exposure resulted in an increase in cell motility, along with an upregulation of the transcription factor glioma-associated oncogene homolog 1 (Gli1). However, treatment with resveratrol inhibited LPS-induced morphological changes, decreased the expression of LPS-induced markers of EMT and inhibited the expression of Gli1, resulting in the inhibition of in vitro cell motility and invasiveness. These results provide a novel perspective for the anti-invasion mechanism of resveratrol, suggesting that the effect is in part due to its ability to inhibit the EMT process through the Hedgehog signaling pathway.

mRNA translation and protein synthesis: an analysis of different modelling methodologies and a new PBN based approach

Background

mRNA translation involves simultaneous movement of multiple ribosomes on the mRNA and is also subject to regulatory mechanisms at different stages. Translation can be described by various codon-based models, including ODE, TASEP, and Petri net models. Although such models have been extensively used, the overlap and differences between these models and the implications of the assumptions of each model has not been systematically elucidated. The selection of the most appropriate modelling framework, and the most appropriate way to develop coarse-grained/fine-grained models in different contexts is not clear.

Results

We systematically analyze and compare how different modelling methodologies can be used to describe translation. We define various statistically equivalent codon-based simulation algorithms and analyze the importance of the update rule in determining the steady state, an aspect often neglected. Then a novel probabilistic Boolean network (PBN) model is proposed for modelling translation, which enjoys an exact numerical solution. This solution matches those of numerical simulation from other methods and acts as a complementary tool to analytical approximations and simulations. The advantages and limitations of various codon-based models are compared, and illustrated by examples with real biological complexities such as slow codons, premature termination and feedback regulation. Our studies reveal that while different models gives broadly similiar trends in many cases, important differences also arise and can be clearly seen, in the dependence of the translation rate on different parameters. Furthermore, the update rule affects the steady state solution.

Conclusions

The codon-based models are based on different levels of abstraction. Our analysis suggests that a multiple model approach to understanding translation allows one to ascertain which aspects of the conclusions are robust with respect to the choice of modelling methodology, and when (and why) important differences may arise. This approach also allows for an optimal use of analysis tools, which is especially important when additional complexities or regulatory mechanisms are included. This approach can provide a robust platform for dissecting translation, and results in an improved predictive framework for applications in systems and synthetic biology.

Genome-wide activities of RNA binding proteins that regulate cellular changes in the epithelial to mesenchymal transition (EMT)

The epithelial to mesenchymal transition (EMT) and reverse mesenchymal to epithelial transition (MET) are developmentally conserved processes that are essential for patterning of developing embryos and organs. The EMT/MET are further utilized in wound healing, but they can also be hijacked by cancer cells to promote tumor progression and metastasis. The molecular pathways governing these processes have historically focused on the transcriptional regulation and networks that control them. Indeed, global profiling of transcriptional changes has provided a wealth of information into how these networks are regulated, the downstream targets, and functional consequence of alterations to the global transcriptome. However, recent evidence has revealed that the posttranscriptional landscape of the cell is also dramatically altered during the EMT/MET and contributes to changes in cell behavior and phenotypes. While studies of this aspect of EMT biology are still in their infancy, recent progress has been achieved by the identification of several RNA binding proteins (RBPs) that regulate splicing, polyadenylation, mRNA stability, and translational control during EMT. This chapter focuses on the global impact of RBPs that regulate mRNA maturation as well as outlines the functional impact of several key posttranscriptional changes during the EMT. The growing evidence of RBP involvement in the cellular transformation during EMT underscores that a coordinated regulation of both transcriptional and posttranscriptional changes is essential for EMT. Furthermore, new discoveries into these events will paint a more detailed picture of the transcriptome during the EMT/MET and provide novel molecular targets for treatment of human diseases.

Establishment of a TGFβ-induced post-transcriptional EMT gene signature

A major challenge in the clinical management of human cancers is to accurately stratify patients according to risk and likelihood of a favorable response. Stratification is confounded by significant phenotypic heterogeneity in some tumor types, often without obvious criteria for subdivision. Despite intensive transcriptional array analyses, the identity and validation of cancer specific ‘signature genes’ remains elusive, partially because the transcriptome does not mirror the proteome. The simplification associated with transcriptomic profiling does not take into consideration changes in the relative expression among transcripts that arise due to post-transcriptional regulatory events. We have previously shown that TGFβ post-transcriptionally regulates epithelial-mesenchymal transition (EMT) by causing increased expression of two transcripts, Dab2 and ILEI, by modulating hnRNP E1 phosphorylation. Using a genome-wide combinatorial approach involving expression profiling and RIP-Chip analysis, we have identified a cohort of translationally regulated mRNAs that are induced during TGFβ-mediated EMT. Coordinated translational regulation by hnRNP E1 constitutes a post-transcriptional regulon inhibiting the expression of related EMT-facilitating genes, thus enabling the cell to rapidly and coordinately regulate multiple EMT-facilitating genes.